I have gotten nearly two dozen emails about it. The media are calling. The amateur websites are going crazy.
All have heard rumors of the potential for severe thunderstorms tomorrow in the Northwest. How much is truth and how much is hype? This blog will examine the situation
The NOAA Storm Prediction Center in Norman, OK is responsible for putting out official severe convection/thunderstorm storm warnings for the US. Their severe storm warmings for tomorrow (Wednesday) predict the main action over the Northwest, which is unusual (but not unprecedented).
They have a 15% chance of hail in the Willamette Valley and SW Washington.
And a 2% chance of tornadoes. Needless to say we are not twister country. But there are typically a few weak tornadoes each year over the region. One even damaged Bill Gates old home in Seattle.
The most familiar measure of the potential for vertical instability is called CAPE, Convective Available Potential Energy. Drop such terms at a party and folks will be impressed.😀
Around here, meteorologists get excited when CAPE gets into the low hundreds. Tomorrow, it will exceed 1000 in some locations. For some perspective, in tornado-alley areas in the midwest, values can rise to 3000-4500.
Here is the NOAA HRRR model forecast for CAPE for tomorrow at 3 PM. Huge values (yellow and red colors), mainly near the western slopes of the Cascades. Wow.
By 5 PM, thunderstorms are breaking out (the white blobs are the upper cloud shields of the storms)
Expect localized heavy rain and gusty winds. And there will be lightning.
At 8 PM, thunder and rain will spread into NW Washington and thunderstorms will be revving up east of the Cascades.
And by 11 PM, boomers will over widespread over eastern Washington
This event will not be unprecedented so I hope the hypesters will keep things realistic.
Where in Western WA is it likely to be the strongest?
ReplyDeleteI used to live in Nebraska Kansas and Missouri. The storms had a certain "feel" when there was tornado potential. The are some decent thunderstorms here but I've not felt that "get to the cellar" feeling here.
ReplyDeleteMost people here don't have storm cellars...
DeleteAnsel and why do you think that is?
DeleteI also know the " feel" having lived in KS. That and various other elements was always a better indication of potential of severity.
DeleteRemarkably muggy afternoon by early spring standards around Bellingham today. I measured a maximum temperature of 68F and a historically warm dew point of 59! It looks like tomorrow may be even worse!
ReplyDeleteis Seattle expected to experience stormy weather before 4pm?
ReplyDeleteThe National Weather Service estimates 6 PM +/- 2 hours for the main front:
Deletehttps://x.com/NWSSeattle/status/1904971239846019538
One acronym not defined. What is HRRR?
ReplyDeleteHigh Resolution Rapid Refresh. It's an hourly model.
DeleteHigh resolution rapid response. It's an hourly model that factors in a bunch of data.
DeleteHigh-Resolution Rapid Refresh. https://rapidrefresh.noaa.gov/hrrr/
Delete...and wow. As I typed this, just felt a MASSIVE thunder peal on Education Hill in Redmond, WA. Wahoo.
High-Resolution Rapid Refresh. A short-term, updated hourly, high resolution model from NOAA
DeleteGoogle is amazing! The High-Resolution Rapid Refresh (HRRR)
DeleteThe HRRR is a NOAA real-time 3-km resolution, hourly updated, cloud-resolving, convection-allowing atmospheric model, initialized by 3km grids with 3km radar assimilation.
One acronym not defined. What is HRRR?
ReplyDeleteHigh-Resolution Rapid Refresh - ie repeated fast computer simulations.
DeleteI had to look it up myself. A quick Google search reveals:
Delete"HRRR stands for High-Resolution Rapid Refresh, a real-time, hourly-updated, 3-km resolution weather model used by NOAA for short-range, high-resolution forecasts, particularly useful for pinpointing severe weather.
Here's a more detailed explanation:
• Purpose: 
The HRRR model is designed to provide highly detailed, short-range weather forecasts, focusing on areas with a high potential for severe weather events.


• Resolution and Update Frequency: 
It operates with a 3-kilometer resolution and is updated hourly, making it a valuable tool for pinpointing localized weather changes.
• Data Assimilation: 
The HRRR model assimilates radar data every 15 minutes over a 1-hour period, adding further detail to the forecasts. "
HRRR is High Resolution Rapid Refresh. It's a short term forecast model.
DeleteNot all gyros wear CAPEs
ReplyDeleteThis made me smile
DeleteLooking forward to it!
ReplyDeleteI also used to live in Nebraska, Iowa, and Missouri. Very familiar with that feel when the little hairs on the back of your neck stand up. I will prepare my dogs for a good old-fashioned hunker-down. They do not like thunder and lightening.
ReplyDeleteSo why is the NWS listing the risk as slight? Latest forecast for CAPE (admittedly from an AI source) is for 1500 - 2500 .
ReplyDelete9:36 AM out here on Vashon Island, it's pouring rain and we've already had some thunder. Woke up to thick fog, too, which still hasn't disspated. This is the Spring weather I really, really, love!
ReplyDeleteMr. Mass, I appreciate your data-driven approach and your clear explanations of what's going on.
ReplyDelete52f on the shores near Alki, Bainbridge Island and Edmonds and 72 in Maple Valley to 80 in Kelso and seeing 82-85 around PDX at 2:15pm! This is an unbelievable spread in temperatures. Only 60f here in the bay in Gig Harbor. Forecast still on track?
ReplyDeleteThe High-Resolution Rapid Refresh (HRRR)
ReplyDeleteThe High-Resolution Rapid Refresh (HRRR)
ReplyDeleteThanks for explaining so much. I was completely unaware of CAPE, etc. As for the action that's headed our way (and as-of 4:42 pm it does seem to be tracking as predicted), we'll find out what Nature has in mind!
ReplyDelete